In view of the limited indoor space and bad quality of outdoor air in some cities, the indoor environment itself has no natural ability to purify. Interior decoration, use of air conditioners and human daily life are continuously discharging volatile organic gases, solid suspended particles, aerosols and other harmful substances, which causes pollution of indoor air and resulting health hazardous. The main indoor pollutants include dust, mold, total volatile organic compounds (TVOC) and other formaldehyde and benzene, and as a result, concern over the quality of indoor air has been growing with improvement of the living standards.
The quality of indoor air may be improved by (1) air filtration: a device for air filtration comprises a fan, and primary-effect, medium-effect and high-effect (sub-high-effect) filters using main filter media of glass fiber, synthetic fiber, asbestos fiber and filter paper or filter cloth made of these fibers, and materials with adsorbability, like activated carbon, to purify the air by filtering the dust and odor, but these porous filter media increase the resistance to the air flow with a filtering effect decreasing over time, and make the air pollution worse or even result in secondary pollution if not timely replaced; (2) electrostatic precipitation: the dust in the circulating air is charged and then the charged dust is collected by a dust collecting device for the purpose of air purification, but this method cannot kill airborne bacteria or remove toxic odor gases like TVOC, and it uses an integrated board not easy to set up and clean; (3) ultraviolet sterilization: ultraviolet rays are used to kill bacteria in the air, which however can do nothing about dust in the air and thus are not able to purify the air; (4) low temperature plasma purification: water molecules and gas molecules in the air are ionized through the strong ionization field generated by a low temperature plasma generator and gas discharge, and active groups of extremely active chemical properties are produced after a series of complex excitation, dissociation and ionization processes, which react with pollutants in the air in a series of complex redox reactions to decompose volatile organic molecules therein so as to purify the air, these radicals also have such a strong inactivation effect for microbes that they achieve the purpose of sterilization while eliminating the organic pollution, and moreover, dust is charged and made heavier through inelastic collision with charged particles so as to be collectively collected and purified.
A plasma air purifier mainly consists of a high voltage power supply and a plasma ionization field. At present, a plasma ionization field may have a structure of a board-to-board type, wire-to-board type, needle-to-board type or wire-to-barrel type. Chinese invention patent CN2688390Y has disclosed a plasma smoke eliminating and dust collecting apparatus having a purifying part consisting of a stainless steel tube, metal molybdenum filaments, a positive electrode plate, and a negative electrode plate, which has technical problems of slow purification speed, unsatisfactory purification effect, and need for assistance of a fan.